Gauge band randomizer

ABSTRACT

An oscillating hauloff device for removing blown film from an extruding apparatus. The oscillating hauloff includes a stacked ring arrangement which provides a compact and stable structure. The turning bars and idler rolls are encompassed in the ring structure and are arranged to cancel effects of web wandering and wrinkling. A method for making the oscillating hauloff, including CNC machining of annealed ring-shaped weldments, that is economical and simple to manufacture. The turning bars are provided with reinforcements that prevent deflection of the turning bars during use. Further the turning bars are provided with flow restricted outlets and axially extending channels to supply uniform air pressure to float the blown film on the turning bars. A specific arrangement for providing utility services to the oscillating hauloff is also disclosed which employs torsional deflection of the loads during rotation of the rings. The oscillating hauloff is suitable for receiving film extruded downwards with only minor adjustments in structure from the unit for upwardly extruded film.

This is a continuation of application Ser. No. 07/831,499, filed Feb. 5,1992, now U.S. Pat. No. 5,360,328.

BACKGROUND OF THE INVENTION

The present invention relates to an oscillating hauloff device forremoving a blown film from an extruding apparatus.

Oscillating haul-offs for removing a blown film from an extrudingapparatus have been known for some time. The major design configurationthat has been commercially successful for many years is an oscillatinghauloff produced by the Windmoeller and Hoelscher (W&H).

Following extrusion of blown film, the film typically is in the form ofa bubble. The sides of the bubble are then forced together when theyreach nip rolls in the hauloff device. As the bubble is passed throughthe nip rolls, thickness variations exist around the circumference ofthe bubble. If this film is wound directly onto a roll, the thickerareas will cause the wound roll to build up faster than the thinnerareas, creating hills and valleys on the wound roll surface. A majorproblem arises when such rolls are taken from the extrusion process andsubsequently unwound and conveyed through converting equipment such asprinting presses, laminators or bag machines.

Uneven rolls considerably reduce the speed of this equipment and thequality of finished product. The unevenness of the roll causes slack insome areas of the film and tightness in other areas which ultimatelycauses creases in the film web. On the printing press, for example, theink will not transfer to the film inside of a crease which degradesproduct quality. These manufacturing processes have to use spreaderrolls or other means in an attempt to eliminate these creases. Theseadditional processing steps complicate and slowdown the process.

In other downstream equipment, the bag machine has several nip rolls inorder to draw the film into the sealing and/or punching area. When thefilm is drawn through these nips rolls any slack area will result infurther creases. If the crease happens to be in a location where a sealis placed, that seal will be defective.

In all cases, the better the roll quality coming from the extrusionline, the faster one can run the downstream equipment and theprobability is increased of producing a better quality product. Whilethe need for improved roll quality has been recognized for some time andthere have been several attempts at solving it, these attempts stillhave a number of deficiencies.

An initial attempt to solve the quality problem utilized a verticaldesign oscillating hauloff. This device had a significant verticalheight requirement; the wider the film, the taller is the oscillatinghauloff and the taller is the required building to house it.

Another problem with the vertical design, is that the film has to goaround several vertical idler rolls which act as an accumulator as theunit rotationally oscillates. As film accumulates, overall output speedslows because some of the film's speed is taken up by the accumulation.The reverse happens when the unit reverses direction, line speedincreases. This results in a variation in line speed that can cause filmwalking in the winder which degrades roll quality.

Other problems associated with subsequent prior art devices include thestability of the unit. One type of oscillating hauloff unit consisted ofa frame having a small diameter shaft suspended from the center. It hadhorizontally mounted idler rolls and turning bars which turned at anglesto one another to effect web direction corrections. The wholeoscillating hauloff unit including all the idler rolls and turning barsas well as the nip rolls and collapsing frame were suspended from thissingle shaft. Any touching of the unit during operation caused it toswing resulting in film wandering and wrinkling. This single shaft alsolimited the size and location of auxiliary equipment such as aircollapsing frames and associated blowers that could be suspended underthe oscillating hauloff. Even if the extra weight could be handled, thesupport shaft would bend and cause misalignment if the load was notequally balanced. Such a machine would not be applicable or would havesubstantial drawbacks if applied to extrusion lines oriented to extrudethe film downwardly.

Another problem which has occurred in prior art devices is uncontrolledwandering of the film. In horizontal designs, there have been twoturning bars which work together to allow for a total oscillation of 360degrees. As with any turning bar, frictional forces cause a slight shiftin axial position as the film passes around its diameter. This is inaddition to the pure geometrical shift associated with its diameter. Itis well understood that the geometrical shift can be negated by properlyoffsetting the turning bar from the center of rotation. However, thewandering due to frictional effects has not been corrected and wrinkleshave been induced. The result is that although normal process gaugevariations are spread evenly over the surface of the wound roll, thewrinkles and associated creases due to wandering are wound into thefinished roll.

Yet another problem of prior art devices is that the turning bars can bepermanently deformed by deflection. This is because turning bars arehollow and lack sufficient rigidity due to the many air outlet holes intheir surface, and thus, over time, forces exerted by the film havedeformed the bars.

Another problem is related to the method for distributing utilities suchas electrical power, water and other pressurized fluids (typically air)that are required during operation of the oscillating hauloff device.Utilities are fed to auxiliary equipment mounted within the movingstructure of the oscillating hauloff using a long umbilical cord whichis folded back and forth while wrapping around the unit +/-180° as theunit cycles. This folding motion stresses the wires and hoses as theyflex and causes long term problems with breakage.

SUMMARY OF THE INVENTION

One aspect of the present invention features stacked, oversized andencompassing support rings that give the oscillating haul-off highstability as well as a very low profile. Stacking the rings one on topof each other is important because it provides a high degree of unitstability suitable for mounting auxiliary equipment and prevents anyundesirable swaying motion which causes web wander and wrinkling. Theserings are made sufficiently large to fully encompass and support theidler rolls and turning bars in positions suitable for use in ahorizontal oscillating hauloff. By fully encompassing the idler rollsand turning bars, a low height for the unit is achieved which is idealfor fitting the unit inside of buildings with height restrictions.

Another aspect of the invention features a method of manufacturing ringmembers with CNC (i.e., computer numerical controlled, which apparatusis well known per se in the manufacturing field) positioned alignmentholes in each ring for establishing the location of idler rolls andturning bars. This is important because they establish the criticalangular relationship between idler rolls and turning bars. CNC equipmentcan locate to tolerances better than two thousandths of an inch. Thisenables an extremely accurate film path to be achieved throughout theoscillating haul-off and minimizes web wandering and wrinkling. A secondbenefit is that these predrilled alignment holes significantly reduceunit assembly time because there is no need for post machiningalignment.

Still another aspect of the present invention relates to the combinationof hollow encompassing support rings with ball bearings between theupper and lower surfaces of adjacent rings to achieve simple andeconomical construction. The rings and ball bearings in combinationprovide for oscillatory motion, accurate positioning and mountingsupport of idler rolls and turning bars, and a hollow channel forrouting the utilities. This simple unitized system is highly economicalsince the rings directly incorporate all required functions into asingle structure and enable all machining to be performed on a singleCNC machine at the same time.

Another aspect of the present invention features passing the web betweenidler rolls and turning bars in a manner that the web approaches asecond turning bar from an opposite direction than the direction inwhich the web approaches the first turning bar. This arrangement ofidler rolls and turning bars substantially cancels the wandering effectof the web as it passes through the oscillating hauloff. This isimportant because there is a natural shift in film position on theturning bar due to friction between the film and the bar. The amount offriction and thus film shifting is related to web tension, filmthickness, etc. By bringing the film web around the second turning barfrom the opposite orientation, the web shifts by the same amount, but inthe opposite direction from the wandering caused by passing over thefirst turning bar, thus canceling the initial shift. This prevents webwander and minimizes wrinkling.

Another aspect of the present invention relates to zero backlash-drivensupporting ring members which maintain precise positional relationshipsrequired for the rolls and turning bars to one another, utilizingchains, sprockets and timing belts. This, in simple manner, achieves thevery critical respective geometries between the idler rolls and turningbars so that the film exits the oscillating haul-off without wanderingback and forth.

The present inventors also discovered that there has been a problemrelated to turning bar design in that additional wrinkles have beencaused by a varying air pressure profile beneath the film as it passesover the bar. One cause for this was found to be due to the arrangementof the drilled hole orifices through the turning bars. The holes inprior devices have been drilled about 1 and 1/2 inches apart from eachother. Directly over each hole there is a localized high pressure areaand midpoint between the holes there is lowest pressure. This pressuredifference which is exerted on the film causes additional wrinkles inthe web.

The second cause for pressure profile induced wrinkles is related to thevolumetric flow of air through the turning bar. A film web is floated(lifted) off the surface of the turning bar by creating pressure beneaththe web sufficient to overcome the effects of web tension. If pressuredrops below float pressure the film drags on the surface of the turningbar causing wrinkles and web wander. The pressure required to float thefilm is proportional to web tension per inch divided by the radius ofthe turning bar and typically is 10 to 20 inches of water for a 3 to 4inch diameter bar. As an oscillating hauloff turns through its cycle,the surface area of the turning bar that the film covers changessignificantly. Minimal coverage occurs when all of the turning bars andidler rolls are lined up. Existing turning bar designs incorporatedrilled hole orifices of diameter large enough to allow significantvolumetric air flow. When these holes are uncovered during some of thecycle, internal pressure is lowered by escape of air. It may go so lowas to be less than that required to adequately lift the film off of theturning bars surface causing wrinkles and web wander.

This air pressure variation is compounded by changes in web size. Thepresent state of the art sought to compensate for the change in filmwidth with plugs located inside the turning bar that can be moved in andout according to the web width that is run. But the plugs are ratherineffective because there still exist the changes in surface areacovered as the hauloff is oscillated. Additionally, the mechanism formoving the plugs usually rusts due to the presence of moisture and endsup having to be left in one position, usually in the widest position,which makes problems worse when narrow webs are manufactured since airpressure is lost from the ends which are uncovered.

Another aspect of the invention features flow restricted air outlets inthe turning bars to maintain uniform film float as changes occur in thesurface area covered by film during the oscillating process. It isimportant to minimize variations in the way the film floats (lifts) offthe turning bars since these variations induce film wrinkles andwandering. Incorporating flow restricting air outlets limits the flow ofair and ensures the minimum internal turning bar pressure is alwayshigher than what is required to float the film. Such restricted airoutlets also allow for an excess pressure to be dissipated across thelength of the orifice so the film float is not affected when operatingat very high internal pressure.

Still a further aspect of the present invention relates to axiallyextending air distributing grooves extending outward from each hole onthe turning bar surface for more uniform pressure distribution andsupport of the film. As discussed above, it has been discovered that itis important to minimize variations in the pressure profile under thefilm since variations will cause unwanted film wrinkling. Directly overeach hole there is a localized high pressure area. By cutting a grooveoutward from the hole and substantially perpendicular to web motion,this pressure is diffused and spread evenly along the film. Thisprevents pressure variations under the film and does not promote wrinkleformation. This feature acts effectively in concert with the restrictedoutlets to achieve uniform lifting over a wide range of operatingconditions.

A still further aspect of the invention features reinforced turning barswhich are mounted to allow axial thermal expansion. This feature isfound to prevent turning bar deflections which cause the film to wrinkleand wander. As film wraps around the turning bar, web tension pulls onthe bar and tends to deflect it. By attaching a backing bar to addrigidity in the direction of the web tension forces, and providing forthermal expansion, the deflection is substantially prevented. Thedimension of the backing bar perpendicular to the direction ofdeflection is kept slightly smaller than the diameter of the turning barso as not to interfere with the film. Deflecting forces due to thermalexpansion of the turning bars are prevented by incorporating slottedends which are free to slide on mounting plates. Film temperature istypically 150 degrees Fahrenheit or more and causes the temperature ofthe turning bar to exceed that of its encompassing ring. By providingthermal expansion slides, the turning bars are prevented from deflectingand causing wrinkling with temperature change.

A further aspect of the present invention features torsionallydeflectable utility leads between a fixed supply and the oscillatingrings. This is important because utility leads which are torsionallydeflected have significantly longer life spans than those that areflexed back and forth. This design limits the torsion to a maximum of 90degrees which is easily absorbed by standard utility leads such aselectrical wiring, air and/or water hoses.

A still further aspect of the present invention relates to a stackedring oscillating hauloff which is capable of being positioned forreceiving blown film in an upward or downward extrusion lineconfiguration. It is important to provide an oscillating hauloffcapability for downward extrusion since this arrangement is desired formany processes and there are presently no oscillating hauloffs easilyadaptable for this purpose. This is accomplished by maintaining the sameframe orientation and reversing the order of the four rings (upside downas a unit). The only required design change is that the ball bearinggroove, previously, the lower surface of the level I ring must insteadbe cut into the upper surface of the level IV ring (before the order ofthe rings is reversed) and the receiving rings are arranged according tothe direction of receiving the film.

A further aspect of the present invention relates to the use of airwhich is substantially free of polymers in the turning bars and therebyavoiding use of factory air which is laden with volatile short chain,sticky polymer molecules that create blockages inside of the orifices ofthe turning bar. This is important because blockage of the orifices willresult in uneven floatation of the film resulting in film wrinkling andwandering. Mounting the blower stationary allows for drawing air fromoutside of the building. This outside air does not contain the stickypolymer molecules and thus does not clog up the turning bar holes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view shown in cross section of the blown filmextruder and oscillating hauloff according to the present invention.

FIG. 2 is a plan view of the oscillating hauloff rotated to 135 degrees.

FIG. 2a is a plan view similar to FIG. 2 illustrating the blown filmdisposed in the oscillating hauloff.

FIG. 3 is a plan view including a section partially broken awayillustrating the oscillating hauloff rotated to the 180 degree position.

FIG. 3a is an enlarged view of a portion of the ring shown in FIG. 3.

FIG. 4 is a side view, shown in cross section, showing the oscillatinghauloff including the driving mechanism according to the presentinvention.

FIG. 5 is an enlarged side view of the drive mechanism of theoscillating hauloff according to the present invention.

FIG. 6 is a plan view showing the ring member of level I taken alongline 6--6 of FIG. 5.

FIG. 7 is a plan view showing the ring member of level II taken alongline 7--7 of FIG. 5.

FIG. 8 is an enlarged view of the mounting of the backing bar to thering member shown in FIG. 7.

FIG. 9 is a plan view showing the ring member of level III taken on line9--9 of FIG. 5.

FIG. 10 is a plan view showing the ring member of level IV taken on line10--10 of FIG. 5.

FIG. 11 is a schematic side view showing the arrangement for providingutilities to the oscillating hauloff according to the present invention.

FIG. 12 is a side view and cross sectional view of the turning bar andbacking bar according to the present invention.

FIG. 13 is a plan view showing a ring member with an enlarged chain andsprocket assembly.

FIG. 14 is a schematic side view shown in cross section of the blownfilm extruder and oscillating hauloff arranged for downward extrusionaccording to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a plastic melt that exits extruder 110 and enters thebottom of a blown film die 112. An annular plastic melt issues from thetop of die 112 and is continually drawn upward by nip rolls 2 and 2athrough cooling ring 114 forming a continuous cylindrical plasticbubble 1. The bubble is converted to a flat sheet of film 1a (also knownas layflat) by passing through collapsing shield 116. The film thenpasses between rubber roll 2a and steel roll 2 which nip together andare motorized to continually pull the film during the extrusion process.The collapsing shield 116 and nip rolls 2 and 2a are attached to ring I(see FIG. 4) which rotates +/-180° about the central vertical axis(herein referred to as the "unit axis") of the bubble 1. It is a matterof general practice within the industry that the film travels aroundsteel roll 2 and not rubber roll 2a. The layflat film 1a exits the niprolls wrapping partially around steel roll 2 and then passes underneathand around idler roll 4 also attached to ring I (see FIGS. 4 and 7). Thefilm 1a then travels horizontally inward towards the unit axis andpasses underneath and around turning bar 6.

Turning bar 6 is fixed and attached via several small brackets to andsupported by backing bar 7 to prevent deflection by film web tensionthereby eliminating this cause of wrinkle formation. Backing bar 7 isslightly thinner vertically than the diameter of turning bar 6 toprevent interference with film 1a. For example, if turning bar 6 is fourinches in diameter then a backing bar 7 which is three inches thick maybe used. The turning bar/backing bar 6/7 is attached to ring II whichrotates +/-135° around the unit axis. Turning bar 6 is mounted offsetfrom the unit axis by a distance of α, wherein α=(π/2 * Turning BarRadius) to prevent geometrical web wandering. Pressurized air issupplied to the ends of turning bar 6 which exits out small holes forproviding a substantially frictionless surface for film 1a to pass over.This will be further described in connection with FIG. 12.

The film 1a then travels horizontally outward and away from the unitaxis passing underneath and around idler roll 8 mounted in ring III. Thering III rotates about the unit axis by +/-90°. The arrangement of idlerrolls 4 and 8 together with turning bar 6 correct for one half of theangular shift in direction of film 1a by this oscillating hauloff unit.The film 1a then travels at a slight downward angle passing through theunit axis, under and around idler roll 8a also attached to ring III. Asthe film 1a passes idler roll 8a, its direction is reversed and ittravels horizontally inward towards the unit axis and passes underneathand around turning bar 10.

Turning bar 10 is attached to and supported by backing bar 11 and theyperform similar functions to turning/backing bar 6/7. Backing bar 11 isattached to ring IV as seen in FIG. 11. The ring IV rotates about theunit axis by +/-45°.

After passing over the turning bar 10, the film 1a travels horizontallyoutward and away from the unit axis passing underneath and around idlerroll 12 which is mounted in a fixed position on to frame 16 as seen inFIG. 2. The arrangement of idler rolls 8a and 12 together with turningbar 10 correct for the remaining half of the angular shift in directionof film 1a. The arrangement of idler roll 8 and 8a cause the turningbars 6 and 10 to be approached by film 1a from opposite directionsthereby effectively canceling the frictional web wandering that hasoccurred on turning bars in prior systems as will be described infurther detail below.

FIGS. 2 and 2a are plan views of the oscillating hauloff with ring Ishown after being rotated 135°. FIG. 2 illustrates the oscillatinghauloff without the film 1a and FIG. 2a illustrates the oscillatinghauloff with the film 1a shown passing over the idler rolls and turningbars.

Ring I is fully supported by frame 16 and its associated cross supports18. The assembly of four stacked rings is held firmly in place byhold-down arms 24, 24a and 24b and rollers 26, 26a and 26b which arebolted to rigid vertical columns 20, 20a and 22. The precise positioningof each ring is maintained by a drive unit (see FIG. 5) including amotor 30 and a gear box 31 that are mounted on a top plate 28. The driveunit is controlled by an electrical panel 92 that is mounted on anothercorner of the frame 16.

As shown in FIG. 2a, the film direction is indicated by direction arrowswhich are dashed if the film is traveling in a path which is hidden fromsight in this view and solid if the film can be seen in this view. Asthe film 1a passes over steel roll 2 it heads toward idler roll 4, asshown by arrow 1. The film 1a then passes underneath and around idler 4and inward as shown arrow 2.

Turning bar 6 is at a relative angle of 33.75° to idlers 4 and 8. Filmwraps 180° underneath and around turning bar 6 and travels outwardtoward idler 8 as shown by arrow 3, for a total turning angle of 67.5°.The film is brought to the opposite side of the unit axis after firstwrapping around idler 8 and travelling through the unit axis as shown byarrow 4. Film then wraps around idler 8a and travels inward as shown byarrow 5 and approaches turning bar 10 from an opposite orientation tothat direction which the film approached turning bar 6. Turning bar 10is at a relative angle of 33.75° to idler 8a. The film 1a then wraps180° underneath and around turning bar 10 and travels outward towardidler 12, as shown in arrow 6, for a second turning angle of 67.5°. Thisyields a total combined shift in web direction of 135° which exactlycompensates for the rotated position of the nip rolls.

As the film 1a passes around turning bars in general, there exists anatural tendency for film to shift position on the bar. These shiftsoccur on turning bars 6 and 10, however the opposite directions of theapproach facilitated by the presence of idler rolls 8 and 8a causeshifts in opposite directions which act to exactly cancel this filmwandering. The combination of angular compensation (135° in this case)and opposite direction of attack on the turning bars allows for the filmto exit the oscillating hauloff on a stationary idler 12 without webwander.

Pressurized air for the turning bars is provided by blower 90 mountedfixed to frame 16. Clean air is drawn from outside of the plant (asschematically illustrated at 91) and is fed to the turning bars viablower 90 thereby avoiding having to use air from inside the plant whichcontains sticky polymers. These polymers have a tendency to plug the airoutlets in the turning bars. It is also contemplated that other sourcesof clean air such as from a suitable filtering system may be used forthis purpose. This air together with other utilities such as electrical,compressed air and water are routed to each level using utility arms100,102,104,106,108 and 110 and these will be describe in detail in FIG.12.

FIG. 3 illustrates the oscillating hauloff rotated to the 180 degreeposition. Drive shafts 36, 38 and pulleys 48, 58, 68 and 78 as well assprocket 70 can be seen. The operation of these elements will bedescribed further in connection with FIG. 5.

FIG. 3a illustrates an enlarged scale section of a ring taken in area Ashowing one of the internal ring supports 84 as well as the grooves cutin the ring for the ball bearings and seals. These internal ringsupports 84 add rigidity to the rings without significant weightpenalties.

FIG. 4 shows the compactness of the oscillating hauloff unit. The niprolls 2 and 2a are suspended from cross members 130 and 130a which arerigidly mounted to ring I. The rigid structure 130 and 130a created forsupporting nip rolls 2 and 2a has sufficient strength and versatility toallow for mounting equipment and the associated framework a processormight select. The nip rolls 2 and 2a can be located at any distancebelow ring I so long as they remain parallel to idler 4.

Idler 4 is fully encompassed by and vertically located in the center ofring I just as turning bar 6/7, idlers 8/8a and turning bar 10/11 areencompassed by and mounted in the center of rings II, III and IVrespectively. Turning bar 6 is located adjacent to idlers 4 and 8/8a andturning bar 10 is adjacent to idlers 8/8a and 12. The center to centerdistance between adjacent rings is calculated by adding the radii of theassociated turning bar and idler roll(s). For instance, if turning barsare 4 inches in diameter and idler rolls are 8 inches in diameter thenthe center to center distance between rings would be (4/2+8/2)=6 inches.This adjacent, stacked design allows for obtaining minimum overall unitheight. The rigidity and versatility of the unit allow for the use ofpre-existing nip rolls and collapsing shields and unit compactnessallows for installation where vertical height is restricted.

FIG. 5 illustrates the drive mechanism of the oscillating hauloff. RingI consists of top plate 81, outer plate 82, bottom plate 83 and internalring supports 84. Internal ring supports are vertical posts at multiplelocations around the inside edge the ring which provide structuralrigidity. Mounting brackets for idler rolls and turning bars areattached to flat machined surfaces inside the rings for properalignment. Ring II, III and IV have similar elements which aredesignated with an "a", "b", and "c" respectively.

Ring II's bottom plate 83a rests on top of ball bearing 88a which restson top of ring I's top plate 81 and both are free to move relative toone another. This arrangement exists between adjacent rings and allowseach to move independently. Frame 16 has included with it a circularplate similar to plate 81 and ball bearing 88 which allows ring I torotate on the frame.

The frame includes a ring hold-down arm 24a which pushes down throughroller 26a on ring IV to hold the rings properly in place on top offrame 16.

Power is transferred from motor 30 into gear box 31 and through driveshaft 32 connecting vertically downward through coupling 33 to shaft 38.Shaft 38 transfers the power through key 41 into sprocket 40 whichengages with chain 86. Chain 86 is disposed around and is attached toring I and thus power driving the sprocket is transferred to the chain86 to drive ring I. Power is also transferred from sprocket 40 throughbolts 44 to pulley 42, timing belt 46 and on to pulley 48, which key 49locks to shaft 36. Shaft 36 powers ring II through key 59, pulley 58,timing belt 56, pulley 52, bolts 54 and sprocket 50 which is mounted onshaft 38 using bearing 51 to allow independent rotation. Sprocket 50engages chain 86a which drives ring II similar to ring I. Ring III isdriven similar to ring II using key 69, pulley 68, timing belt 66,pulley 62, bolts 64 and sprocket 60. Ring IV is driven similar to ringsII and III using key 79, pulley 78, timing belt 76, pulley 72, bolts 74and sprocket 70. Pulleys 48, 58, 68, and 78 provide for gear reductionand yield a speed ratio of 4:3:2:1 for rings I, II, III and IVrespectively. Pulleys, timing belts, sprockets and chains are usedbecause they exhibit zero backlash and therefore act to precisely locateeach ring and maintain their critical angular relationships whichprevents web wander and wrinkling.

FIGS. 6, 7, 9, and 10 are top views of each ring. FIG. 6 shows ring I towhich is attached nip rolls 2 and 2a via support beams 130 and 130a,idler roll 4 and utility arm 110.

FIG. 7 shows ring II to which is attached turning bar 6 via backing bar7 and utility arm 108.

FIG. 8 illustrates the connection for mounting the backing bar 7 to ringII taken along area B in FIG. 7. This mounting of the backing bar allowsaxial thermal expansion because of slot 122 which allows mounting plate120 to slide back and forth as the turning/backing bar heats up and thusthis prevents turning bar deflection.

CNC located hole 124 is precisely drilled in plate 120 and ring II andprecision surface 128 is machined into the ring II which act togetherwith bolts 127 and 128 to provide very accurate positioning of thebacking bar 7 and thus of the turning bar 6. Low deflection turning barsand accurate positioning act independently to prevent web wander andwrinkles. CNC machines are used to similarly locate all idler rolls andturning bars.

FIG. 9 shows ring III to which is attached idler rolls 8/8a and utilityarms 104/106.

FIG. 10 shows ring IV to which is attached turning bar 10 via backingbar 11 and also shows utility arm 102.

FIG. 11 is a side view of the utility distribution system. Utilitiesincluding electrical, water and air services are required for properoperation of oscillating equipment. Starting at stationary frame 16, theutilities are attached to utility arm 100 which brings the utilitiesinward toward the unit axis. Just prior to reaching the unit axis,utility arm 100 ends and the now free, torsionally deflectable utilityleads 140 and 140a arc separately downward to utility arms 102 and 104and twist +/-45° and +/-90° respectively about the unit axis as thehauloff oscillates. This twisting action is readily absorbed by theutility leads and is far superior to folding action which tends to breakthem over time due to fatigue.

Utility arm 102 is attached to ring IV and holds pressurized air hosesfor turning bar 10. These hoses are routed within the structure of therings between plates 81c, 82c, 83c and internal ring support 84c toeither or both ends of turning bar 10 (the backing bar can also act as aplenum for the turning bar).

Utility arm 104 is attached to ring III and holds all services requiredfor lower levels. Services are routed around ring III through theinternal ring structure, 180° and pass into attached utility arm 106.Utilities are arranged within utility arm 106 and pass inward toward theunit axis. Just prior to reaching the unit axis, utility arm 106 endsand the now free, flexible utility leads 140b and 140c arc separatelydownward to utility arms 108 and 110 and twist +/-45° and +/-90°respectively about the unit axis as the hauloff oscillates.

Utility arm 108 is attached to ring II and holds pressurized air hosesfor turning bar 6. These hoses are routed similar to ring IV.

Utility arm 110 is attached to ring I and holds all services required bythe nip rolls 2 and 2a and any other auxiliary equipment attached toring I.

FIG. 12 shows side and cross sectional views of axially extending airdistributing channels or grooves 146, 146a and 146b extending outwardfrom each hole 144, 144a and 144b in the surface of turning bars 6 and10. These small holes and axial channels provide for more uniformpressure distribution and support of the film and significantly reducewrinkling. Air flows out through the hole in the center of the channelwhich has a diameter small enough (between about 1/32 and 3/32 of aninch) to restrict the flow to a minimum yet allow pressure to exert onthe film. The film acts like a seal on top of this channel and due tothe depth of the channel, air is free to distribute itself. The channeltypically does not extend the full length of the turning bar since airwould leak out at the edges of the film. Interruptions in the grooves(ie. providing a plurality of channels) allows for the pressure to besealed in and are thus more effective at floating the film. Other typesand shapes of channels are possible and are contemplated.

Backing bar 7 and 11 are attached to turning bar 6 and 10 respectivelyusing "C" spacers 141 which have a channel (about 0.010 inches) slightlydeeper than that required to mate with the turning bar. This arrangementallows for a securing bolt to screw through clearance hole 148 and intothreaded hole 149 pulling the turning bar snugly into the channelproviding for turning bar rigidity. There are a multiplicity of "C"spacers 141 arranged along the length of the bars and each spacer isfixed to the backing bar by screws 142 and 142a. Access is provided tothe securing bolts via holes 143 drilled opposite to holes 148 in therespective backing bars 7 and 11.

FIG. 13 shows a plan view of a typical ring member with chain 172 andsprocket 174 enlarged relative to the ring member 170 for clarity. Chain172 wraps around and is rigidly attached to the ring and is engaged bysprocket 174. As sprocket 174 turns, chain 172 causes the ring to bedriven with zero backlash afforded by the proper mesh of sprocket 174and chain 172.

FIG. 14 shows a blown film extrusion line with an oscillating hauloffarranged for downward extrusion. Plastic melt exits extruder 310 andenters the top of a blown film die 312. An annular plastic melt issuesfrom the bottom of die 312 and is continually drawn downward by gravityand nip rolls 202/202a through cooling ring 314 forming a continuousplastic bubble 201. The bubble is converted to layflat film 201a bypassing through collapsing shield 316. The film then passes betweenrubber roll 202a and steel roll 202 which nip together and are motorizedto continually pull the film during the extrusion process. The functionof this oscillating hauloff arrangement is the same as described in FIG.1 except the rings are inverted with ring I on top and ring IV onbottom. Ring IV is allowed to rotate on frame 316. All components withinthe oscillating hauloff function the same and are numbered similar toFIG. 1 except 200 has been added to each reference numeral in FIG. 1 forthe components in FIG. 14. The film 201a exits underneath frame 316 andis processed in the normal way.

The present invention has been described in connection with certainstructural embodiments and it will be understood that variousmodifications can be made to the above-described embodiments withoutdeparting from the spirit and scope of the invention as defined in theappended claims.

What is claimed is:
 1. An oscillating hauloff device for a blown filmline wherein an assembly of idler rolls rotatably shift theirrelationship to one another and to a turning bar over time in apredetermined manner to enable flattened film trained there-over to havegauge variations distributed back and forth across the width of theflattened film,that improvement wherein; said hauloff device comprises aplurality of ring members sized to surround the path of film to beproduced by the blown film line, said ring members being stacked to restupon each other, each said ring member being relatively rotatable withrespect to its adjacent ring member, at least one selected ring membercarrying a said idler roll and at least one other selected ring membercarrying a said turning bar, each said idler roll and each said turningbar being of a length fitting within its respective ring member andlocated so that the plurality of stacked ring members substantiallyencloses said idler roll and turning bar, and a drive mechanism engagedwith the exterior of said ring members for producing said relativerotation between said idler roll and said turning bar.
 2. An oscillatinghauloff device as defined in claim 1, further comprising means fordriving said ring members with substantially zero backlash.
 3. Anoscillating hauloff device as defined in claim 2, wherein said means fordriving said ring members includes a respective chain secured to aperipheral surface of each said ring member and a respective sprocketdisposed for driving said chain attached to said ring member.
 4. Anoscillating hauloff device as defined in claim 3, further comprisingtiming belts and pulleys for driving the sprockets at differentpredetermined speed ratios.
 5. An oscillating hauloff device as definedin claim 1, further comprising torsionally deflectable utility leadsdisposed between fixed supply means and said ring members for supplyingutilities such as power and pressurized fluid to the oscillating hauloffdevice, said leads arranged so that rotation of said rings relative tosaid fixed supply means is accomplished by torsional deflection of theleads.
 6. An oscillating hauloff device as defined in claim 5, whereinsaid utility leads are supplied radially inwardly from said fixed supplymeans to substantially the center of the oscillating hauloff device andthen are directed radially outwardly to selected ring members.
 7. Anoscillating hauloff device as defined in claim 6, wherein said utilityleads are carried on a first, fixed support member toward the center ofthe oscillating hauloff device and are carried on a second supportmember attached to and rotatable with one of said ring members forsupplying said utility leads to said ring member, said first and secondsupport members being separated in the direction of the axis of the ringassembly to accommodate rotation therebetween and allow torsionaldeflection of said utility leads during rotation of said ring members.8. An oscillating hauloff device as defined in claim 1, wherein thedimensions of said idler roll and said turning bar in the direction ofthe axis of said ring members is, for the idler roll, greater than theaxial depth of the respective ring member, and is, for the turning bar,less than the axial depth of the respective ring member, said dimensionsselected to prevent interference, during movement of the ring members,between adjacent idler roll and the turning bar.
 9. An oscillatinghauloff device as defined in claim 8, further comprising ball bearingsdisposed between upper and lower surfaces of adjacent ring members,enabling the oscillating hauloff device to have a low profileconstruction.
 10. An oscillating hauloff device as defined in claim 1,further comprising ball bearings disposed between upper and lowersurfaces of adjacent ring members, enabling the oscillating hauloffdevice to have a low profile construction.
 11. An oscillating hauloffdevice as defined in claim 10, wherein said ball bearings are formed byupwardly facing and downwardly facing surfaces of adjacent ring membersthat have machined grooves defining ball bearing races and ball elementsconfined in said races.
 12. An oscillating hauloff device as defined inclaim 11, wherein said ring members comprise welded metal members thatform a hollow channel weldment, said weldment being in a stress relievedstate, said ball bearing race being formed in the surface of the stressrelieved weldment.
 13. An oscillating hauloff device as defined inclaims 1 or 10 further comprising machined alignment holes in the ringmembers for mounting said idler rolls and turning bar, said holes beingprecisely positioned with respect to the axis of rotation of said ringmembers, the position of said holes providing a precise angularrelationship between idler roll and turning bars on respective ringmembers.
 14. An oscillating hauloff device as defined in claim 1,further comprising nip rolls connected to an uppermost ring member forreceiving blown film from an extruder disposed above said hauloffdevice.
 15. An oscillating hauloff device as defined in claim 1, furthercomprising nip rolls connected to a lowermost ring member for receivingblown film from an extruder disposed below said hauloff device.
 16. Anoscillating hauloff device as defined in claim 15 disposed with saidblown film line in a relatively closed space and, further comprising ameans for providing air to said turning bar from a relativelycontaminant-free source outside of said closed space.
 17. An oscillatinghauloff device as defined in claim 1, wherein at least one turning barincludes a plurality of flow-restricted outlets each including alongitudinally extending distribution channel disposed in the outsidesurface of the turning bar and constructed and arranged to distributeair along the surface of the turning bar substantially transverse to thedirection of travel of the blown film line.
 18. An oscillating hauloffdevice as defined in claim 1, wherein at least one turning bar includesa backing bar disposed adjacent to the outside surface of said turningbar and constructed and arranged to reinforce said turning bar againstdeflection under tension applied by the film to the turning bar.
 19. Theoscillating hauloff device of claim 1 comprising a set of at least foursaid ring members, a first of said ring members, closest to said filmline, supporting a tube-collapsing device and a set of power driven niprolls, and carrying a first idler roll positioned to have film trainedthereabout from said nip rolls, a second of said ring members carrying afirst turning bar about which said film is led and taken away atrespective corresponding angles within a given angular range, the filmbeing led from said first idler roll about said first turning bar, athird of said ring members carrying at least a further idler roll, aboutwhich film from said first turning bar is trained, and a fourth of saidring members carrying a second turning bar about which film is led andtaken away at respective corresponding angles within said given angularrange, the film being led from said further idler roll about said secondturning bar, said ring members being continually rotated within rangesof motion that decrease by a standard decrement from one ring member tothe next, beginning with said first ring member, said decrementcorresponding to said given angular range.
 20. The oscillating hauloffdevice of claim 19 wherein at least one of said ring members carried twoidler rolls positioned on opposite sides of the axis of rotation of saiddevice about which said film is trained to pass across said axis, andutility leads for said nip rolls extend along a path comprised ofsubstantially radial segments, substantially axial segments and at leastone circular segment within a respective ring member, in a patternavoiding interference with the varying film path.
 21. The oscillatinghauloff device of claim 19 wherein said turning bars have a plurality offlow-restricted air outlets for providing air-lubrication to filmtrained thereabout, there being air conduit means following the path ofsaid utility leads for said nip roll until reaching the respectiveturning bar, said air outlets having a diameter between about 1/32 and3/32 of an inch, said outlets being effective to restrict the volume ofair flow required thereby to limit the size of said air conduit means.22. The oscillating hauloff device of claim 19 wherein there are four ofsaid ring members and said given angular range is +/-45 degrees.
 23. Theoscillating hauloff device of claim 19 wherein said drive mechanism isconstructed to drive each of ring members in continuous, dependentoscillatory motion relative to all other ring members in said set. 24.The oscillating hauloff device of claim 23 wherein the number geometryand distribution of said air outlets are selected to provide effectiveair lubrication of said turning bar without detrimental air pressuredrop along the length thereof.